Translations:Vitamin B12/13/en

Definition

Vitamin B₁₂ is a coordination complex of cobalt, which occupies the center of a corrin ligand and is further bound to a benzimidazole ligand and adenosyl group. A number of related species are known and these behave similarly, in particular all function as vitamins. This collection of compounds is sometimes referred to as "cobalamins". These chemical compounds have a similar molecular structure, each of which shows vitamin activity in a vitamin-deficient biological system, they are referred to as vitamers. The vitamin activity is as a coenzyme, meaning that its presence is required for some enzyme-catalyzed reactions.

• adenosylcobalamin
• cyanocobalamin, the adenosyl ligand in vitamin B₁₂ is replaced by cyanide.
• hydroxocobalamin, the adenosyl ligand in vitamin B₁₂ is replaced by hydroxide.
• methylcobalamin, the adenosyl ligand in vitamin B₁₂ is replaced by methyl.